CALCULATION OF OVERBROKEN VOLUME FOR UNDERGROUND OPENING IN JOINTED ROCKMASS

The definition of overbreak and Relation between unstable block's volume and overbroken volume are discussed, and the methods to calculate block's position and volume are summed up to 3 kind: stochastic, determinate and half-stochastic, and instruction is put forward for further study on overbreak. The determinate calculation about position of the block incised by 3 joints, especially the hidden dangerous block are discussed and settled, and a simple method to calculate the block's volume approximatively is advanced. The overbreak calculation is instructionally significative in safe and efficient underground opening construction.